a. Field of the Invention
The instant invention relates to localization systems, such as those used in cardiac diagnostic and therapeutic procedures. In particular, the instant invention relates to a system and method for registering the coordinate system of the localization system to the coordinate system of an externally generated model or image data set.
b. Background Art
It is known to generate a heart chamber geometry in preparation for cardiac diagnostic or therapeutic procedures. Often, a mapping catheter is introduced into the heart chamber of interest and moved around within the heart chamber, either randomly, pseudo-randomly, or according to one or more preset patterns, in order to capture a cloud of location points. The three-dimensional coordinates of the mapping catheter are typically measured using a localization system (sometimes also referred to as a “mapping system,” “navigation system,” or “positional feedback system”). The localization system measures the coordinates of the mapping catheter within a localization field, typically by relating a characteristic of the localization field, such as a voltage, experienced by the mapping catheter to a location of the catheter within the field. A surface model of the heart chamber geometry may then be generated by wrapping a surface around the cloud of location points.
In some instances, it is desirable to augment the localization system model of the heart chamber geometry with an external image or segmented model of the heart chamber. For example, it is known to utilize a CT or magnetic resonance image of a patient's heart to assist cardiologists or other clinicians in performing an electrophysiology study or cardiac ablation treatment. These three-dimensional images of the heart help the clinician to visualize the location of a medical device, such as an ablation catheter, within the patient's heart, thereby improving efficacy of treatment. Further, such three-dimensional images advantageously provide additional detail about the heart chamber geometry that may not be available with the model generated from the localization system standing alone.
The localization system may also be utilized to detect the position of another object, such as an electrophysiology or ablation catheter, within the localization field. It may be desirable to depict the position of the object, as measured by the localization system, on the three-dimensional image. However, the three-dimensional images typically do not utilize the same coordinate system as the localization system. Thus, the position of the object, as measured by the localization system, cannot be directly displayed on the three-dimensional image. Further, non-linearities and inhomogeneities in the localization field may introduce error if an affine transformation is used to transform the position of the object, as measured by the localization system, to a position on the three-dimensional image.